1. Field of the Invention
The present invention relates to a method for manufacturing monolithic ceramic electronic components. More specifically, the present invention relates to a method for manufacturing monolithic ceramic electronic components used for producing the electronic components such as a monolithic capacitor by laminating ceramic green sheets.
2. Description of the Prior Art
FIG. 10 illustrates a monolithic capacitor as one example of a monolithic ceramic electronic component forming part of the background of the present invention. The monolithic capacitor 1 includes a plurality of internal electrodes (not shown) within a ceramic unit 2, and on opposite ends thereof, a pair of external electrodes 3 are formed which are connected electrically to the internal electrodes.
For preparing such monolithic capacitor 1, the following method has been utilized hitherto. A plurality of rectangular electrodes are formed previously on a plurality of ceramic green sheets, which are then compressed by a pair of rigid press molds after being laminated. In the process of compression by the rigid press molds, the laminated green sheets are placed in the lower press mold, and then the green sheets and the internal electrodes are compressed together by pressing the upper press mold so as not to leave any gap between the various green sheets and electrodes. In this case, if there were any gap, a delamination might occur in a subsequent cutting or baking process, so a large pressure is required for pressing.
After lamination by pressing, the laminated green sheets are cut and chipped into the shape of rectangular parallelepipeds, and the external electrodes are formed on the opposite ends thereof after being baked.
Since the sheet thickness differs between the portions where the internal electrodes are formed and where they are not formed, when using the rigid press mold for compression, the molding density of the portions where the opposite internal electrodes are not superposed tends to remain low, so there is a problem in that delamination may easily occur in these portions. Particularly, the more the number of green sheet laminated increases, the larger the density difference in the pressing, thus exerting a great influence. Accordingly, when producing the multi-layer monolithic capacitor, the prior art process results easily in defective products due to the short pressing, thus considerably deteriorating the yield.
Moreover, since the pressing method by the rigid press molds causes distortion of the molds when applying the pressure, the acting force differs with the point of action of the upper and lower molds, thus resulting in a non-uniform pressure force which also causes the eventual delamination.
Furthermore, when compressing by the rigid press molds, since the chips or the ceramic units after baking are formed in the shape of generally perfect rectangular parallelepipeds, the external electrodes formed thereon may project outward from the ceramic unit due to their thickness, so that there is a problem in that their mounting characteristics on a substrate will be deteriorated.